Cinematographic apparatus



Patented Jan. 30, 1923.

UNITED STATES PATENT OFFICE.

WALTHER BAUERSFELD, OF JENA, GERMANY, ASSIGNOR TO THE FIRM OF CARL ZEISS, OF JENA, GERMANY.

CINEMATOGRAPHIC APPARATUS.

Application filed August 13, 1921. Serial No. 492,130.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

To all whom it may concern:

Be it known that I, \Vaurnnn BAUERS- FELD, a citizen of the German Empire, re-

siding at Jena, Germany, have invented a" new and useful Cinematographic Apparatus (for which I have filed an application in Germany, March 17, 1919; Switzerland, May 19, 1920, Patent No. 89256; Austria, May 26, 1920; England, June 26, 1920, Patent No. 146210; Italy, July 10, 1920; and France, September 18, 1920), of which the following is a specification.

The present invention relates to a device for the optical compensation of the movement of the film for use in a cinematographic apparatus for projection or for taking photograms having a uniformly traversed film, which device contains rotatable and controlled by the film actuating means a ring of objectives, the axes of \v iich are parallel to the axis of rotation of the ring. The employment of such a ring of objectives has been proposed for the purpose of avoiding the mechanical difliculties which arise when employing a band of objectives moving parallel to the film. However, whilst the use of such a band of objectives, when several film-pictures are projected simultaneously, involves but a very slight displacement of the pictures produced on the screen (viz, one equal to the pitch of the objectives), the said displacement becomes considerable when employing a ring of objectives, it being the greater, the more the circular path of the centres of the objectives deviates from the rectilinear ath of the centres of the film-pictures. owever, according to the invention it may be reduced to an amount approximately as small as that resulting when a band of objectives is employed, which end is attained by optically transforming the rectilinear path of the centres of the film-pictures during their passage through the field of the rays into a path which to all intents and purposes is with suflieient accuracy circular, and coincides with the path of the centres of the objectives. For this purpose between the ring of objectives and the film a rin of rhombic prisms, or central reflectors, is isposed, also rotatable and controlled by the film actuating means, the surfaces of entrance and emergence of which prisms or reflectors are perpendicular to the axis of rotation of the ring, the said axis of rotation being parallel to that of the ring of objectives.

In the annexed drawings: Figs. 1 and 2 show a view in elevation and a section in plan respectively of a constructional example of the inventionin which between the ring of objectives and the film a ring of rhombic prisms is disposed. Fig. 3 shows diagrammatically (by way of a projection on the film-plane) the transformation of the rectilinear path of the film-centre during its passage through the field of the rays into a well-nigh circular path by means of rhombic prisms. Figs. 4 and 5 show a front view in elevation and a section in plan respectively of a second constructional example'oi' the invention in which between the ring of objectivcs'and the film a ring of central reflectors is introduced into the path of the rays. Fig. 6 shows diagrammatically (by Way of a projection on the plane of the reflected image of the film) the transformation of the rectilinear path of the film-centre during its passage through the field of the rays into a well'nigh circular path by means of central reflectors.

In Figs. 1 and 2 the ring a the shaft 6 of which is rotatably disposed, contains at its periphery 20 evenly distributed objectives a", the axes of which are parallel to the shaft 1). The ring 0, the shaft 11 of which is rotatably disposed in such a manner that it is parallel to the shaft b of the objective-ring a, contains 12 rhombic prisms c contiguous to one another, the surfaces of entrance and emergence of which are perpendicular tothe shaft (1. The film is marked e, and the film gate The respective direction of travel of the two rings and of the film is indicated by arrows. The rings are to be supposed to be coupled with the actuating mechanism of the film in such a manner that a like number of prisms, of objectives and of film-pictures move through the field of the rays in like spaces of time. Besides the following lettering has been adopted 1' is the distance from the axes of the objectives to the shaft 1), and n is the displacement which is imparted to a ray entering a rhombic prism perpendicularly to the surface of entrance of the said prism.

The respective value of r, and n is deter mined by the condition, that the rectilinear path of the film-centre during-its pasage through the field of the rays becomes by means of the rhombic prisms transformed into a path, which is for all practical. purposes with sulficient accuracy circular, and coincides with the path of the centres of the objectives. In Fig. 3 of the drawing M denotes the axis of the ring of objectives and M, the axis of the ring of risms. P, lying in the centre of the field 0 the rays {hence coinciding with the centre of the film ate denotes the centre of a film-picture, which centre by means ofarhombie prism becomes displaced in the direction of a diameter of the ring of prisms by the amount n, and imaged in the centre 0 of: an objective. When travellin from the centre to the margin of the fie'l of the rays, the film-centre P covers the distance (half the pitch of the film), and reaches P In the same time the objective-centre reaches 0,. In order to attain that also at the margin of the filed of the rays the image of the film-centre P is formed in the objective-centre 0,, it is neces sary that P 0 (as well as 1 ,0 be equal to a. From this uirement there result for the calculation 0 the values r, and n the approximate equations:

to the film-point which becomes imaged in 0 lies at P, O P bein equal in value to n, and inclined to M M5 theangle me. If, as it is desired, the film-centre travellin along the straight line P 1, is to be image invariabll in t e objective-centre during its passage 1; rough the entire field of the re s, it is necessary that Plies on the straight line P,P,. Supposing a rectangular system of coordinates be laid through M the X-axis n.0, of which system; is perpendicular ,P then, as will be inferred from Fig. 3 of e drawing, the following equati? holds good as re rds the straight line I with respect to he said system'of coordinates: z =r,-n=constant. As a matter of fact, however, the points P form a curve for which according to Fig. 3 of the drawing the following equation holds good:

.rzr cos o -n cos mo. Taking into account the values for r, and n,

as previously stated, and m== the follow- P ing equation results zz (Z cos Z cos g?)- If this latter equation Z and Z, be replaced by their respective values: Z =20, and 2,:12, in accordance with the appertaining first constructional example, the resulting values for m, within the limits 9:0 and e max.=%=9, will lie within the limits 95.993 mm. and 96.001' mm., whilst for ca there results the value 96 mm. Hence, the eatest distance of the various points P m the straight line P,P,, and even the relative distance of the points P which are ituated farthest away to the left and ri ht min the straight line P,P,, amounts to ess than 1/100 mm, which may be considered to be negli 'ble.

In Figs. and 5 the lettering corresponds, as far as this is admissible, with that of the first example. The ring a contains 24 ohjectives a the axes of which are pa allcl to the axis of rotation b of the ring. I ring 9, shaft 1:. of which is rotatably disposed so as to be parallel to the axis b of the objective-ring 0, contains to central reflectors contiguous to oneanother, the surfaces of entrance and emerg nce of which are perpendicular to the shaft h. Between the film e and the ring g of the central reflector there are introduced into the path of the rays two simple stationary reflecting prisms i and i, the reflecting surfaces of which are parallel to one another, and inclined to the surfaces of entrance and emergence of the central retuating mechanism of the film in such a manner that a like number of central reflectors, of objectives, and of film-pictures pass throu h the field of the rays in like spaces of time. Furthermore, the -following lettering has been adopted: r denotes the distance from each objective-axis to the axis 6, and r, the distance from the corner of each central reflector to the shaft k.

The respective value of r, and r. is determined by the condition, that the rectilinear path of the filmcentre during its passe through the field of the rays becomes y means of the central reflectors transformed objecti'v'z In Fig.1 6 of the drawing lL'denotes theaxis of e ring of objectives, and M; the axis of the ring of central reflectors. P lying in the centre of the field of the rage denotes the centre of a single picture of e refl image e, and becomes by means ofa central reflector in the centre 0 of an objective. S, denotes the corner oi the said central reflector, which corner, as is known, lies midway between P", and 0,. When travellin from the centre to the mar gin of the fiel of the rays, the centre P,

which is inclined to M, M by'tl1e.angle mand the following equation holds good:

F g-=36. If, asit is desired, ,the film-center travelling along the straight line PfP, is to be imaged invariably in the objectivecentre during its passage through the entire field of the rays, it is necessary that P lies on the straight line P,'P,'. Supposi n rectaniilar system of coordinates be fiiid throng M the X axis mm is perpendicular to P5, supposin her that lines arallel to the Y-axis o the said svstem o coordinates are drawn thro h P", S and O, which lines intersect the -axis in I S, and 0. respectively,

of he film-Picture covers the distance i being equal to S000! and the (half the pitch of the film), and reaches P, In the same time the objective-centre 0 reaches 0,, and the corner S- of the central reflector reachesS In order to attain that also at the margin of the field of the rays the image of the centre P, of the film-picture is formedin the objective-centre 0, it is necessary that P,S be equal in S,d,, and furthermore, that I 8,, and 0, lie in a straight line. Fromt uirement there result for the calculation of e values 1-,, and 7-, the approximate equations z i *1 I ZF'Z.

angle mp, m being equal to the filmpoint which becomes imaged in 0 lies in the locus of P, whilst the corner of the central reflector lies in the locus .of S. Besides P, S and 0 lie in a straight line ":im zP iI" If in this latter equation Z and Z. be replaced by their respective values: 2 :24, and Z,=40, in accordance with the rappertaining second oonstructurel example, a resulting values for :0, within the limits :0

and e max.= =15, will lie within the limits 47.997 mm. and 48.008 mun, whilst for 1-, there results the value 48.000 mm. Hence, the greatest distance of the various 2 ing' letteringbe adopted: P.,'S =s, ,,=p,

and M.,M.=,a, then, as will be inferred from F ig; 6 of the drawing, the following e notion holds good as regards the straight inc P fP, vwith respect to the said system of coordinates:

3.,13- P101. In this equation -2r g Inserting the values thus obtained as well as the values for r, and r, as previously stated in the said equation or on, there results the following equation As a matter of inch-however, the points P form a curve, for which according to Fig. 6 of the drawing the following equation holds good:

I 01:1 cos ip-2P. In this equation pzr, cos e+a-'r, cos me.

Inserting the value thus obtained as well as the ctive values for 1-,, 1-,, a, and m, as prevlously stated, in the equation for w, the following equation holds good:

z: os zeta-2.)]

1. In a device for the optical compensation of the movement of the film for use (PL 0) of which in a cinematographic apparatus having a. uniformly traversed' film, a ring of-ob ectives rotatably disposed, the axes of'which objectives being parallel to the axis of rota:

tionof the ring of ob'ectives, a ring ofoptical elements rotate le about an axis parallel to that of the ring of objectives, which ring of optical elements is to be disposed between the said ring of objectives and the film, whereby each of these optical elements is of such a kind as to been able of displacingsn entering my parallel y to itself, these optical elements having, in addition, ,such a distance apsrt that their surfaces of entrance sindemergence are perpendicular to the axis of rotationof the ring containing them and whereby. the said ring of objectives and the ring of optical elemerits are destined to experience '0. rotary motion, depending on the filni motion.

2'. In a device for the optical compensa-' tion of the movement of the film for use in a cinematographic apparatus haying a unithe film, the surfaces of entrance :incl

emergence of which rhoinbic prisms being perpendicular to the axis of rotation of the ring of prisms, whereby the said ring of objectives and the said ring of prisms are destinedto'experience a i-ohiry motion, de-

pending on the film motion.

WALTHER BAUERSFELD. \Vitnessesz PAUL Km'icen, RICHARD HAHN. 

